Foreign key migration

Am using Erwin to do some modelling and have some newbie questions. I'm a bit confused about the principles and best practises for key migration with identifying and non-identifying relationships.

Basically, as far as I can tell, if you determine that a parent entity cannot be null, a relationship is considered identifying. An example might be invoiced items relating to an invoice. This means that the key for invoiced items will include the invoice id.

My confusion is that if you have a parent entity that itself has a number of child entities (which each have their own children), migrating the foreign keys to all the children seems to be an awful lot of duplication of data which I didn't think was itself particularly good practise.

Is this just how it has to be to ensure referential integrity?

A secondary question is whether determining whether a relationship is identifying or not is purely a business logic decision, or is there some other rule?

Thanks all.

Tom Received on Wed Feb 19 2003 - 19:37:15 CET